1. Field of the Invention
The present invention relates to a method and apparatus of fabricating a thin film transistor array substrate, and more particularly, to a method and apparatus of fabricating a thin film transistor array substrate, which is capable of reducing fabrication time owing to a simplified fabrication process.
2. Discussion of the Related Art
Generally, a thin film transistor array substrate (hereinafter, referred to as “TFT array substrate”) includes a switching device or a thin film transistor, wherein the switching device controls an operation of each pixel in a flat type display device such as a liquid crystal display device or a light-emitting display device, and the thin film transistor drives each pixel in the aforementioned flat type display device.
The thin film transistor is comprised of a gate electrode, a semiconductor layer formed to be insulated from the gate electrode, source and drain electrodes formed to have a channel region on the semiconductor layer, and a pixel electrode formed to be electrically connected with the source electrode.
A process of fabricating the TFT array substrate includes a photolithography process.
The photolithography process is comprised of a photoresist coating process, a drying process, an exposure process, a development process, a heat treatment process, and an etching process.
In order to improve an electrical conductivity between the semiconductor layer (a-Si) and the source/drain electrodes for the fabrication process of the TFT array substrate according to the related art, an ohmic contact layer (n+ a-Si) is additionally formed between the semiconductor layer and the source/drain electrodes. In this case, If the ohmic contact layer is connected between the source and drain electrodes, the ohmic contact layer functions as a conductor, whereby the thin film transistor is not driven. For the fabrication process of the TFT array substrate according to the related art, the ohmic contact layer positioned between the source and drain electrodes (which corresponds to a channel region of the thin film transistor) is removed by a dry etching process after patterning the source and drain electrodes through the use of a wet etching process. During the dry etching process, the source and drain electrodes serve as a mask for etching the ohmic contact layer.
However, the related art method of fabricating the TFT array substrate has the following disadvantages.
First, the fabrication process is complicated and the fabrication time is increased due to the patterning process using photolithography.
Also, since the ohmic contact layer is selectively etched through the dry etching process, an inaccurate etching for the ohmic contact layer may cause a problem of over etching, whereby the semiconductor layer may be damaged due to the over etching.
Due to the damage on the semiconductor layer, the yield of the thin film transistor is lowered.
As the ohmic contact layer is selectively etched by the dry etching process, the increased fabrication time causes deterioration of productivity.
Since the pixel electrode is electrically connected with the source electrode by photolithography, the fabrication process is complicated and the fabrication time is increased, thereby lowering the yield.